Virtual machines (VMs) are widely used to create virtualization. VMs operate based on the computer architecture and functions of a real or hypothetical computer. A VM is a software implementation of a machine that executes programs like a physical machine. A single physical machine may support multiple VMs executed thereon and manage these VMs using a program called “hypervisor.” Traditional VM architecture causes resource waste because a guest operating system (OS) has to be deployed for each VM.
Containers provide lightweight virtualization that allows for isolating processes and/or resources without the need of providing instruction interpretation mechanisms and/or other complexities of full virtualization. Container technology, such as Linux Container (LXC), provides lightweight virtualization that allows isolating processes and resources without the need to provide instruction interpretation mechanisms and other complexities of full virtualization. Containers effectively partition the resources managed by a single host operating system (OS) into isolated groups to better balance the conflicting demands on resource usage between the isolated groups. That is, the container technology allows sharing a common OS and possibly some appropriate binary files or libraries.
Docker is an open-source project that automates the deployment of applications inside software containers by providing an additional layer of abstraction and automation of operating-system-level virtualization on Linux. (Note: the term(s) “Docker” and “Linux” may be subject to trademark rights in various jurisdictions throughout the world and are used here only in reference to the products or services properly denominated by the marks to the extent that such trademark rights may exist.) Docker uses resource isolation features of the Linux kernel such as cgroups and kernel namespaces to allow independent “containers” to run within a single Linux instance, avoiding the overhead of starting and maintaining virtual machines.